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Forget Better Batteries, Nothing That Exists Or is in Development Can Store Energy as Well, And as Cheaply, as Compressed Air (theconversation.com)
An anonymous reader shares a report: The concept seems simple: you just suck in some air from the atmosphere, compress it using electrically-driven compressors and store the energy in the form of pressurised air. When you need that energy you just let the air out and pass it through a machine that takes the energy from the air and turns an electrical generator. Compressed air energy storage (or CAES), to give it its full name, can involve storing air in steel tanks or in much less expensive containments deep underwater. In some cases, high pressure air can be stored in caverns deep underground, either excavated directly out of hard rock or formed in large salt deposits by so-called "solution mining", where water is pumped in and salty water comes out. Such salt caverns are often used to store natural gas. Compressed air could easily deliver the required scale of storage, but it remains grossly undervalued by policymakers, funding bodies and the energy industry itself. This has stunted the development of the technology and means it is likely that much more expensive and less effective solutions will instead be adopted.
I guess some places are air tight, but the rock where I live if full of holes and I could only imagine would leak profusely.
I know no ones ever read the fucking article, but what if there is not even a linked article ??
Sorry, had to
Look up Shingeki no Kyojin for more info on the amazing potential of compressed air. Don't believe me? Watch this.
This seems unlikely to replace batteries at the small scale. Even discounting the risks of puncture or leakage in mobile devices like cell phones or computers; the equipment necessary to compress air into containers can likely only be scaled down so far before it loses efficiency.
Plus every air compressor I've ever seen or worked with is pretty loud. Maybe there are ways to reduce the noise; but this ultimately seems like more of a large scale way to store energy produced via solar or wind power than a replacement for traditional batteries.
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There is no “minimum storage pressure” but the economics are poor for anything lower than 50bar. For CAES with tanks, the economics push you towards pressures of 200 - 250 bar. In caverns, the pressure you can use depends on the cavern depth. 120bar is not unusual. For a cavern with 120bar storage pressure that was allowed to swing down to (say) 70bar when “discharged”, you would be storing ~23MJ in each cubic meter of cavern. Thus for 1GWh (3.6 million MJ), you would need 156,000 cubic metres of cavern. That is actually a relatively small salt cavern! If it was a sphere, it would have radius of 33.4m. Surprising as it may seem, most salt caverns in existence are bigger than that!
I remember the Indian compressed air cars too, was wondering what happened to those...
"There is more worth loving than we have strength to love." - Brian Jay Stanley
This is not a quote I find anywhere in TFS, TFA, or in any of the articles linked from TFA.
There are a lot of ways to store wind and solar, all of which are somewhat underutilized. Pumped hydro (where water is pumped uphill) is an alternative, as are giant flywheels spinning in a vacuum with magnets on the rim. There are a lot of alternatives to batteries that are in active use.
NOWHERE, other than in the headline, is the claim made that compressed air is SUPERIOR to any of these other "alternative to batteries" technologies.
NOWHERE is there even a direct comparison made to batteries, other than a passing (and unsubstantiated) reference that "batteries work well for short term storage" with an implicit comparison that CAES is more suited to longer term storage.
Where the heck did this headline come from? Citation needed.
When you compress air, the temperature goes up. This heat then dissipates into the environment. That is undoubtedly some of the energy used to compress the air, so you've lost some efficiency there.
You know, the stuff most people directly use every day?
Flappinbooger isn't my real name
Compressed Air Energy has one major drawback. If there is a problem it could cause an explosion. And unlike from chemical energy storage such explosions cannot be monitored and cutoff as quickly.
I once had a tanker truck drive by me, and at the same time, the tanker had buckled inwards a dent (probably from pressure differences from changing altitude) I needed to stop my car and inspect it, because that little buckle felt like something had hit my car from that pressure wave.
There is a lot of danger in compressed air.
This can be mitigated with proper maintenance and monitoring. But this is the same with nuclear energy, Companies don't want to do it, because it costs money that cuts into its profits, and governments don't want to do it, because the Tax payers need to pay for it.
If something is so important that you feel the need to post it on the internet... It probably isn't that important.
nothing that exists or is in development can store energy as well, and as cheaply, as compressed air
The curious might ask for some references that prove this point.
More information from the author of the study...
Turnaround efficiencies are mis-reported for CAES. If you think about pure electricity-in-electricity-out storage, then it is certainly possible to beat 70% even at small scale and at large scale you are likely to get 80% (if you do all the right things with management of heat).
CAES does always involve managing heat but nobody with any sense would store pressurised air hot. Yes air does tend to rise in temperature when you compress it but all of the serious proposals for CAES systems remove the heat from the air before storing the air. For good performance, you store the heat (separately) and use it later on during the air expansion. Apart from the fact that temperatures would weaken or destroy the air containment, they would also mean that you stored a lot less air (by mass) in the same containment. The pressurised air containment is the most expensive part of most CAES systems so you want to work this as hard as you can.
Energy is banked as potential energy by moving massive chunks of concrete up an incline via rail. Later on, the chunks are coasted back down the incline, reintroducing the energy into the electrical grid. >80% efficiency!
Not sure about the thermodynamic efficiency difference of producing high pressure air vs. liquid air, but in terms of volume efficiency, liquid air may be a better choice. There are a lot of applications of gasses that have been turned to liquids and allowed to escape at atmospheric pressure. The escaping gas might be hooked up to a small generator to make electricity that could power some devices for charging batteries or other uses.
In a time of universal deceit, telling the truth is a revolutionary act. George Orwell
Or just build the world's largest whistle.
politicians are like babies' nappies: they should both be changed regularly and for the same reasons
All you have to do is observe the heat cast off by such a process from compressor to storage to know this to be a dubious claim. The greater the storage pressure, the worse the efficiency becomes. Never mind the challenges, expense, and hazards involved in implementing and maintaining pressure bottles. If you're free to concern yourself solely with energy density, as in this case with HPA then, you might as well bring nuclear fission--the gold standard for energy density--back on the table.
Two of my imaginary friends reproduced once
...but what we really, really, really need is storage for vehicle propulsion. Still a battery, or maybe a supercapacitor, is required.
Mostly material, reliability and size.
I am not sure if any of you remembered some rather unpopular toys from the 1980's. They where pneumatic powered creatures. where you pumped them up 20-30 times. flip a switch they would walk/drive/hop for about 30 seconds. They had these tanks on them the size of 4 D sized batteries. Which they would have the energy to power such action for hours.
If you were to fill them up too much the tanks would break, and the toy will be broken.
Now the energy of the 30 pumps gave more energy then such movements onto a generator to charge a battery. But there were a lot of tradeoffs.
Moving parts wear out, a tank that is dealing with changing rising and dropping pressure forces will need to be monitored and maintained, enough room will need be made for to safely hold and store the tanks.
If something is so important that you feel the need to post it on the internet... It probably isn't that important.
Ask you need is one leaky hose or device to screw up whatever efficiency the might be. Ever use air hoses in a shop? And people aren't going to absorb the costs of super close tolerance machining on every part to get around this. The practicalities of this make it stupid. Critical thinking is required.
-- I ignore anonymous replies to my comments and postings.
How about gravity/weight energy storage? No need for airtight containers, the only danger is at the bottom of the tunnel/shaft, etc. Probably at least on par with the energy storage and cost of compressed air, maybe even better.
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Saw a pie chart a day or 2 ago that shows natural gas and coal are about equal now in the US market. And since natural gas is now cheaper than coal to build and run, US use of coal will continue to diminish. That, BTW, is the absolutely best way to replace polluting sources, by replacing them with cheaper things that don't pollute. IOW, don't pass a law against something, pass a law that helps create cheaper but cleaner resources and no, that doesn't mean subsidize something, because that is just the people paying more for something through taxes. No, REALLY make it cheaper - make something that is intrinsically cheaper. That's now natural gas. Hopefully some smart guy will build the 90% efficient solar cell, and these guys will perfect their air compression technique and we'll get 100% clean power.
What's the best way to move from coal to natural gas outside the USA? By fracking the F out of the oceans of natural gas reserves that the USA has, and selling it to the furriners... Its a win-win - they get cheaper electricity and the world gets less CO2 and other nasty shit in the air. Trump just did that by harrassing Angela Merkle, the German prime minister, into canceling her country's gas pipeline to Russia, and instead building liquified natural gas seaports for import of LNG by ships from... the USA. We better get to fracking every square inch if we want to reduce pollution.
Having worked with a lot of air compressors over the years I was suspicious of this as an efficient way to convert energy into a storage medium. After a quick Google I found a blurb on a manufacturer's website that up to 90% of electricity used to run a compressor is converted into heat.
https://www.quincycompressor.com/the-benefits-of-efficient-air-compressors/
I'd imagine that large-scale compressors are more efficient, and there would be some heat capture employed to utilize the energy lost there, but can this really compete?
I worked on a project doing exactly this about 5 years ago. The company, called SustainX, i believe is gone and disbanded. There are probably others too. They basically took a giant marine diesel engine and modified it become an air compressor in storage mode, and an expander in retrieval mode. They had solved some of the technical challenges of doing it in a thermodyanically efficient way. Something about isothermal and adiabatic. I forget the details but they have some elaborate mechanism for *both* the compression and expansion of the gas to extract a lot more usable energy. The big problem was storage. They used a giant tank array for their test system. They really wanted to deploy it globally but it turns out there's only a few locations in the entire word that have suitable geology for underground storage. So since tanks were relatively expensive and the geology wasn't prevalent, the company didn't sell anything and folded. Cool idea and very technically savvy company though.
Scott
23MJ of gasoline is about 1 litre, so by volume, gasoline has 1000x the energy density.
https://en.wikipedia.org/wiki/...
CAES can only be cost-effective when built on top of an existing disused mine in the appropriate type of rock. We still need better batteries for all the places where you might need electricity and don't have a convenient abandoned mine to convert. Mobile applications come to mind.
Great idea for pushing a plastic bottle a few hundred feet into the atmosphere.. but I wonder how much compressed air it would take to push a car 250 miles, or to produce a KWh of electricity, and how much energy it would take to create that much compressed air. I suppose one could find out from a SCUBA compression station.
Ah yes. 2 years of pchem comes rushing back.. Let's see if PV = nRT then.. oh.. it's gone again.
23MJ of gasoline is about 1 litre, so by volume, gasoline has 1000x the energy density.
https://en.wikipedia.org/wiki/...
Now you just need a process for converting electricity into gasoline, and your energy storage is complete. You can do that with pressure: take some sort of vegetable matter, compress for a few dozen millions of years, and you get gasoline which you can then put into your cavern where it is available for the next cycle.
What could go wrong? An obvious long-term investment.
Well, the storage promised isn't exactly "miraculous". It's well within the bounds of what is physically possible given the mechanism proposed.
But generally speaking your best bet with no information at your disposal is to always against anything new. That limits you to safe investments returning normal profits. How do you beat that? By being better informed than the next investor. Unfortunately every tech investor and entrepreneur thinks he's going to beat the odds, but the odds are what they are because most of them are going to fail.
Ralph Waldo Emerson once said, "Nothing great was ever achieved without enthusiasm," but what he should have added is that no great fiasco is possible without enthusiasm either. Tempering enthusiasm with judgment is probably the toughest thing about developing a new technology.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
You know, those were I need a steel bottle and noisy generator to use compressed air as energy source? No? So maybe do _not_ forget about new battery tech?
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
... the obvious, existing, efficient, works today, energy storage. Pump water up-hill. Release it downhill. Low tech. Massive storage amounts with a big enough reservoir. In use at multiple sites in California, often just to make money on power arbitrage (ie, San Louis dam, reservoir, and fore-bay).
Air is free and renewable, and doesn't need to be transported from where it is pumped from the ground over thousands of miles, and it doesn't need to be refined.
Other than the infrastructure, there is little resource cost, since it's not (yet) a commodity.
Now, does this make the article right? I'm not qualified to say that. But this guy is a professor of Dynamics, and is far more qualified than me.
In terms of storage of energy, and what you have to do to get there, it sounds like nobody is saying it's cheaper/more energy dense than gasoline, they're saying you can generate it and store it cheaply, and tie it in with other sources to smooth out the power generation and consumption.
By the time you're talking about tech with a long-life, over time it seems entirely reasonable the incremental cost at the end of that life is pretty damned small once you have it up and running.
You also get the added benefit you can fill your compressed air with pretty much any energy source, and save that power for later. Link a couple of sources together, and the usual whining about "but what about when it's dark outside" goes away.
What's the energy efficiency of an air compressor? What's the efficiency of the generator the compressed air drives later? What massive volume of space do you need as an air tank to make this even remotely practical? What pressure is necessary to make it practical, and how safe is it in reality to store massive amounts of compressed air at that pressure? Sounds incredibly lossy to me.
This isn't anything new, and not any kind of scientific analysis. This is a wishful thinking opinion piece on a technology that has yet to be proven economically viable.
So, how many silly ideas are we going to have to shoot down before we come to a realization that we already have a solution with decades of proving itself economically viable, reliable, incredibly safe, and effectively unlimited? That would be nuclear power by the way.
These air storage facilities would be incredibly large infrastructure projects, likely taking decades to pay off, and add no real energy generation capacity. If we put that same effort into real world energy production, like wind, hydro (which doubles as storage), and nuclear, then we'd be far more ahead than trying to turn wishful thinking into something viable.
I am armed because I am free. I am free because I am armed.
I'm all for gasoline, and I use it twice a day, but it's not really a reversible process. I want a solar-powered machine that generates liquid fuel from atmospheric water and CO2.
There are some clever ways (i've seen with my own eyes) to make the compression and expansion isothermic and adiabatic. A traditional air compressor does neither. Don't think of these systems as simply giant air compressors. They are much more clever and involve various subsystems and perhaps even additives to the air.
Scott
Seems all energy storage methods have pros and cons and this one seems to not be superior across the board from the replies I’m seeing. I remember seeing years ago compressed air as an energy storage type for cars. What I’m thinking though is it seems this method would make a really great adjunct storage solution where you need cooling. You have to add heat back in to get the efficiency back up, seems server farms could make great use of the added cooling. Maybe electric cars in warmer climbs would also benefit from an alternate AC powered by compressed air which also generates some extra watts as well.
Letter To Iran
I can see it at carefully-controlled and isolated power plants, but NOT in consumer products. It's one thing to have a phone battery catch fire; but compressed air could instantly blow body parts off. I could lose a few pounds, but hopefully not by this method.
Table-ized A.I.
Hopefully some smart guy will build the 90% efficient solar cell,
They do keep getting better. Only a matter of time now before solar becomes the cheapest solution for electrical power generation. Not that useful for blast furnaces and the like, but we could probably live with that (IIRC, "primary thermal" is around 20% of power consumption).
Socialism: a lie told by totalitarians and believed by fools.
Gas is less polluting than coal, but it's still not clean. It could be regarded as the less of two evils, just a stopgap until truly sustainable and non-polluting technologies are more viable.
Even better, that company owner probably doesn't appreciate the difference between 14 psi (Hyperloop) and 14,000 psi (energy storage to power a city). He can try using the same type of materials for both and see what happens.
For scale, dynamite (TNT) will create a pressure wave of around 500 psi @ 2 meters. A truck bomb will destroy a building 50 meters away with a 100 psi pressure wave.
Now you just need a process for converting electricity into gasoline, and your energy storage is complete.
There was a DOE research program to do something like that (with several patents owned by the US government, so effectively open) using hydrogen. Hydrogen storage in metal hydrides has remarkable energy density, not too far from gasoline. The plan was to use very small, pump-able spheres, so you could drain/fill your tank with very similar infrastructure to gas.
Steam hydrolysis is technically over 100% efficient if you're starting with waste steam from power generation (it reclaims some of the heat of fusion of steam, which would otherwise be wasted), so this approach to energy storage has no efficiency loss as long as the "filling" is co-located with power generation.
Socialism: a lie told by totalitarians and believed by fools.
What you describe is the value proposition for plant-based ethanol. It's a complicated machine, yes, but that's what it does.
(And no I don't mean corn. Whatever idiot thought we should make fuel-hooch out of that needs to reconsider their career choices.)
I believe that with adiabatic compressed air storage http://energystorage.org/advanced-adiabatic-compressed-air-energy-storage-aa-caes the design goal is about 70% round trip energy efficiency, which is comparable with, just slightly lower than, li-ion battery systems once you factor in thermal-management energy requirements of the latter. That is, if you have a big li-ion batter bank in a container, you have to heat and cool it depending on the season and climate etc.
Retaining 70% of generated wind energy and PV energy for off-hours use is a very economically valid prospect. If thinking continent-wide, just build 42% more wind farms and PV arrays than you otherwise would need and you're golden. That's cheap as borscht.
Where are we going and why are we in a handbasket?
Every time you compress air, it is heated. The heat is lost energy. Every time you release air pressure, the air is cooled. More lost energy. No mention by the author, no analysis of the amount of lost energy. Bullshit article.
"Eve of Destruction", it's not just for old hippies anymore...
The beauty of this is that you can also use the Heat as well as the Work.
when compressing it will get hot, so use this for heating hot water. And when you release it things get cold. So chill your beer.
Some drink at the fountain of knowledge. Others just gargle.
minus the lead. minus the low energy density.
Some drink at the fountain of knowledge. Others just gargle.
Someone proposed putting a large bag of air under lake Ontario and filling that. I can't find the study. Best places are either next to a large city (Toronto), nuclear plant (Pickering or Darlington) or wind generation. The sealed bag meant they could use clean, low humidity air. Not sure how they solved the heat problem (compressing the air makes it hot, if you lose the heat then you lose a high percentage of your energy. Ontario doesn't have the political competence to make this viable though. Maybe it would work on the US East coast?
https://www.scientificamerican.com/article/new-flywheel-design/
The whole device is contained in a vacuum-sealed steel box with about the same footprint as a household refrigerator, only a bit shorter. The flywheel itself is about 66 by 66 centimeters in height and diameter, and weighs about 340 kilograms.
Not quite sure of the motives, who knows these days what could set someone off.
Personally it's nice as a writer to have validation that someone cares deeply about your work, however I do apologize to the rest of you for the visual interruption of Slashdot's pristine flow of intelligent banter (yes that was a joke haha).
Until he tires or locks on to some other target for the transgression of liking non-pink Starbursts, I amuse myself by thinking of how I make the little monkey dance with each post. For the readers I would suggest they frame it that way, watching him twirl for our enjoyment.
"There is more worth loving than we have strength to love." - Brian Jay Stanley
Every set includes the empty set, so technically there is a linked article and it is sucks---like the vacuum it is.
Also, the OP spouts hot air, like the empty claims asserted.
High Compression Air Powered Vehicles - accident....*boof* pressure tank integrity failure and all the occupants along with those in neighboring vehicles are instantly frozen to death as solid icecorpsicles.
Would Carbon Dioxide make more sense? It turns to liquid around 800PSI, so the stored volume is greater and it doesn't require increasing the pressure to store more energy (just increase the volume).
Finally, when you extract it you can make La Croix sparking soda's for an entire town's water supply at no cost.
Some drink at the fountain of knowledge. Others just gargle.
Just what I was wondering. See a post I made above. If you compress the air to 100 PSI, it'll come out at around 600 C. You'd want to cool it to around room temperature, call it 0 C. Thing is, at that point you're essentially storing the energy as heat, not pressure, aren't you? Why not just use the electricity to melt salt and be done with it?
I'd bet this might be more efficient to extract or compress too. Since the whole operation would be running at a constant pressure you could optimize the turbines or whatever is used for a specific pressure rather than have ones that have to operate across the range 300bar to 70 bar with the same efficiency. The pressure is low enough and the volume small enough that above ground storage in tanks instead of deep caverns is possible. So presumably lower losses. You could even pipe the liquid to where you wanted to expand it.
Some drink at the fountain of knowledge. Others just gargle.
The advantage of petroleum is that the energy density is relatively high. Batteries aren't nearly as high. Liquified natural gas is not as high. Compressed natural gas is much lower. Hydrogen is much lower in energy per volume vs petroleum. (Which is a shame, as hydrogen byproducts from fusion plants on the coast might be a really cool solution.)
But the lowest energy per storage volume of any of these is compressed air. Ok I guess in situations when you either have HUGE, cheap, airtight storage spaces, or very modest energy requirements, you might find a situation where such a solution would be viable. But the whole thing sounds like a late night conversation between drunk college students.
From the wiki on the Tata, the compressed air automobile:
Compressed air has relatively low energy density. Air at 30 MPa (4,500 psi) contains about 50 Wh of energy per liter (and normally weighs 372g per liter). For comparison, a lead–acid battery contains 60-75 Wh/l. A lithium-ion battery contains about 250-620 Wh/l. The EPA estimates the energy density of gasoline at 8,890 Wh/l; however, a typical gasoline engine with 18% efficiency can only recover the equivalent of 1694 Wh/l. [...]
In order to increase energy density, some systems may use gases that can be liquified or solidified. "CO2 offers far greater compressibility than air when it transitions from gaseous to supercritical form."
So one possibility is to use compressed CO2. Generate CO2, compress it, then release it to generate electricity.
No, wait... What problem were we trying to solve again?
Oliver's law of assumed responsibility: If you're seen fixing it, you will be blamed for breaking it.
Every human comes with its own compressed gas mechanism. We just need to hook a hose from our butts to our cellphones!
Have you been on twitter lately? Apparently this is already standard practice.
Oliver's law of assumed responsibility: If you're seen fixing it, you will be blamed for breaking it.
And how is that natural gas going to be liquefied? And what is going to power the ship that transports it across the ocean? And what about when Trump decides to put export fees or such on the natural gas?
https://en.wikipedia.org/wiki/Inverted_totalitarianism
This assumes an adiabatic process. That means that you cannot loose any heat form the compressed air. So the storage tank would have to be insulated in a vacuum Dewar not practical or very expensive. A system that stores compressed air in a non adiabatic way, just about all the systems in existence, are only about 25% efficient. This really sucks compared to batteries.
The Tomy Space Pets. I remember them well. I had the Hoomdorm and one other, but can't recall what it was called. Good times.
"Gas is less polluting than coal, but it's still not clean". Neither is solar, wind ,nor hydro. Your statement is that "Gas is not magic" is noted and well understood.
Have you been on twitter lately? Apparently this is already standard practice.
Okay that was good. Mods c'mon.
sigs are for losers (except to point out that sigs are for losers)
Export fees are unconstitutional.
"No Tax or Duty shall be laid on Articles exported from any State.
ARTICLE I, SECTION 9, CLAUSE 5
Otherwise, you have to transport it somehow, and that's the best we can do. The ship would do well to convert to NG power if it is hauling it regularly. Maybe it already is. I don't know.
Most Scuba tanks are aluminum and are pressurized up to 3,000 psi. Some Scuba tanks are steel and pressurized up to 3,500 psi. Scuba tanks are used in corrosive salt water and filled with compressed air from many different small shops. There are rare instances of tanks failing, but purpose built storage tanks would not be banged around on dive boats, immersed in corrosive salt water or filled with improperly dehydrated compressed air, and so would be quite unlikely to fail.
Power tends to corrupt, and absolute power corrupts absolutely.
The key problem with compressed gas is heat. As you compress it, the gas gets hot, and as the gas gets hot, it gets harder to compress. This can easily reduce your efficiency to 10% if you are not careful.
There are two solutions: quasi-isothermal compression and expansion, which requires is complicated.
Or you store heat and pressure separately, and recombine them again when you want to use the energy. Storing heat is possible, but by no means trivial.
It may take a long time before compressed air is competitive with pump storage.
They only let you use that 20% off coupon for 1 item, no matter how much begging and pleading you do. Wait, maybe if each engineer had their own coupon...
Hi! I make Firefox Plug-ins. Check 'em out @ https://addons.mozilla.org/en-US/firefox/addon/youtube-mp3-podcaster/
Scuba tanks also require an annual visual inspection, and must be shipped off for a hydrostatic test every 5 years.
Except they got promoted. It's pretty much a requirement to win the Presidency, between Iowa's first -in-the-nation caucus and the great corn states' electoral votes.
Your ad here. Ask me how!
If only we could harness the hot air created by all these "policy makers"...
it can be a little better than that, where compressed air is 15% efficient. in other words 85% of energy is wasted. those of us who work in industrial engineering know that fact. it's a lousy energy storage system, to thing some "greenie" would advocate it is hilarious.
Hmm, didn't know that about export taxes, whether the Supreme Court would agree that an export fee in the name of national security is a tax remains to be seen, but judging by some of their other rulings such as Congress being free to write laws abridging speech in the name of national security or infringe on the right to own arms in the name of the children, who knows.
It still takes a lot of power to liquefy and transport that way compared to a pipeline and it has got to the point where America is as unpredictable as Russia and seems to be heading for more of a war footing. Germany would be smart to do both, import by ship and pipeline
https://en.wikipedia.org/wiki/Inverted_totalitarianism
It is marketing by Seamus Graham. That is very likely the AC that submitted this link.
I prefer the "u" in honour as it seems to be missing these days.
is even more efficient!
I said I saw a pie chart that said that coal and natural gas were producing electricity approximately equally in the USA. I can't know whether or not it is correct. I don't know what the pie chart measured or what your reference is measuring, I just said I saw such a pie chart.
Do either or both of these measurements restrict themselves to energy produced for electricity only, or is the coal expended in smelting iron also included in one or the other? Is coal used in cement production - not sure - and if so, was it measured by either source? Don't know again, but we're producing a whale of a lot of cement. Wait, a quick google search says, "Coal is used in cement production." Ding ding ding, winner winner chicken dinner. That'd be a whale of a lot of coal. Does the pie chart measure that and the quoted website not measure it? I don't know.
I'm not lying, I just said I saw a pie chart. Its just one way to look at the question, and I still think I'm correct that coal will continue to diminish and natural gas will continue its ascendency because it is cheaper for electrical production.
You just need to manage a thermal sink, i.e. a circulating relatively large volume of water, so that your compressed air and uncompressed air end up at similar temperatures.
Lead-acid batteries are very good under certain conditions, like short time scales and no weight costs. The question is whether there are other technologies that are better at slightly or significantly longer times scales.
So, yeah, if you are storing electricity that you know you are using tonight, probably lead-acid is the way to go. But is it really the best way if you are saving for a cloudy day a week away? Two weeks? That is what this system is shooting for.
You just need to manage a thermal sink, i.e. a circulating relatively large volume of water, so that your compressed air and uncompressed air end up at similar temperatures.
And that's where I start to get confused on the physics. It probably would help if I'd taken thermodynamics.
So, can you help me out? If I compress a bunch of air, the resulting gas is smaller, under higher pressure, and hotter than it started. How much of the energy I put into compressing the gas went into heating it up? If I cool it down to its original temperature, what happens to the pressure? And once cooled down, how much energy do I get back by releasing it? Do I have to re-heat it before feeding it into a turbine?
(Here's my thought experiment. If I want to compress a volume of gas by 10x, I can increase the pressure by 10x or reduce the temperature to one tenth of the original. Either way, I think you wind up with a smaller volume of gas. But in the second case, the gas won't be under any pressure so if you vent it, nothing much will happen. Well, you'll get fog because the gas is at 30K and potentially has turned to liquid, but let's assume we're talking helium so that didn't happen. So in that case, all the energy was removed as heat and that's what you'll use to run a generator.)
What I'm getting at is whether the compressed gas is necessary. You could just take the electricity and heat something up: a pool of water or a tub of molten salt. If I need to have a water bath to hold and move the heat, maybe we should just skip the gas compression and expansion entirely. Does that make any sense?
Thanks.
Version 2.0 will significantly increase energy density by compressing methane.
Bob Stein, http://bobste.in